This invention relates to the preparation of p-bromo-o-alkylanilines by brominating o-alkylanilines.
Para-brominated o-alkylanilines, such as 4-bromo-2-methylaniline, have utility as intermediates in the preparation of herbicides, insecticides, fungicides, and plant growth regulators. A difficulty in brominating o-alkylanilines is that the aromatic ring of the anilines is usually polybrominated when reacted with bromine because the amino group of the aniline is highly activating. In addition, brominating o-alkylanilines with bromine can sometimes result in the bromination of the side chain substituents or the production of undesirable amounts of o-brominated o-alkylanilines, which are unacceptable as intermediates in certain applications.
Onaka, et al. describe in Selective Monobromination of Aniline Derivatives by Use of Bromine Adsorbed on Zeolite 5A, Chemistry Letters, No. 11, pages 2007-2008 (1984), The Chemical Society of Japan, a process which is said to obtain good selectivity in producing p-brominated-o-aniline. The process includes brominating aniline by use of molecular bromine adsorbed on Zeolite 5A.
The present invention resides in a method of selectively preparing high yields of p-brominated-o-alkylanilines.